2-METHYLPENTANE CATALYTIC REACTIONS ON PT(3-PERCENT-WT)-HNA-BETA-ZEOLITE - KINETIC-STUDIES

The system Pt(2.9 wt%)-HNa beta zeolite is an interesting catalyst for hydrocarbon reforming. Kinetic studies of 2-methylpentane reaction on this catalyst were performed. Apparent activation energies and reacti on orders versus respectively temperature and partial pressures of hyd rogen and hydrocarbon allowed us to explain the bifunctional behavior of this catalyst and to determine the respective function of the plati num and of the support. The reaction orders versus hydrocarbon do not vary with reaction temperature and are positive (+0.6+/-0.1), but the reaction orders versus hydrogen increases when the temperature increas es from -0.3 at 160 degrees C to 0 at 200 degrees C. There are two gro ups of apparent activation energy values differing by about 10 Kcal/mo l. The superior values are obtained for higher partial pressures of hy drogen or hydrocarbon (25+/-2 Kcal/mol) and the lower ones for lower p artial pressures of hydrogen or hydrocarbon (16+/-2 Kcal/mol). The rea ction process would be at the metal-support interface. The adsorption step of 2-methylpentane would be a reative (associative) adsorption st ep followed by a dissociative step of dehydrogenation leading to the m ost abundant surface intermediate (MASI). This kinetic process explain s the experimental values.